1. Field of the Invention:
This invention relates to driving devices for moving the photographic lens barrel of a camera stepwise.
2. Description of the Prior Art:
The devices of this kind generally operate in such a manner that prior to making an exposure, the lens barrel is axially moved forward to focus on an object to be photographed, and after the exposure is completed, it is further moved forward until one cam moves away from the follower on the lens barrel so that the lens barrel is set in the initial position of the next cam and at the same time the drive circuit is rendered inoperative.
In the conventional devices of this kind, to minimize the time lag from the actuation of the release button through the focusing movement of the photographic lens to the start of opening of the shutter, there is a need for the ratchet to turn the distance adjusting ring at a high speed. As the number of cycles of reciprocating operation of the ratchet per unit time increases, however, the problem of increasing the possibility of occurrence of a faulty operation wherein the distance adjusting ring turns two ratchet teeth in one cycle of reciprocating operation by the inertia of the ring becomes serious.